1. Field of the Invention
The invention relates to apparatus including normal and standby processors and, more particularly, to such apparatus providing hot standby operation. The invention also relates to a method for providing hot standby operation with normal and standby processors.
2. Background Information
U.S. Pat. No. 5,794,167 discloses a rail transport microprocessor based reliability system for monitoring and controlling actuators as a function of data supplied by sensors. The system includes at least two parallel microprocessors handling the same application. The microprocessors receive pre-encoded data from the sensors and microprocessor output data. A third, comparison microprocessor, known as a voter, employs software to compare the encoded characteristic results of the respective parallel microprocessors.
U.S. Pat. No. 4,181,945 discloses a high-reliability vehicle control system including two redundant computer systems. Each of the computer systems consists of two computers, which compare their results and deliver them only if they agree. Which one of the two computer systems processes telegrams received from a control center and compiles telegrams to the control center from messages of on-board units is determined from the control center. At regular intervals, switchover to the other computer system is effected to check whether the latter is functioning correctly or not.
U.S. Pat. No. 6,281,606 discloses a plural output electric train control station, which employs a data processor for monitoring and controlling signals generated at a plurality of transformer-driven power output terminals.
U.S. Pat. No. 5,751,569 discloses a method of controlling railroad train movement over a layout of railroad track, which is defined geographically using a linear network of geographic control objects. A train control process may be distributed (e.g., not requiring a single central processing unit) and lends itself to localized testing when a failed hardware module is replaced, as only the function performed by that module need be tested.
U.S. Pat. No. 5,301,906 discloses an Interlocking Control System (ICS), such as the Microlok® railroad interlocking control system for railroad switching and signaling. A signal to move a switch to its normal position, for example, may be produced in three controllers. Input/output signals regarding entrance and exit locations in a shared territory are transferred between a control console and a terminal block over a data communication link. This information is further transferred in parallel fashion between the controllers and terminal block over respective data communication links. Signals to and from the field are respectively transferred in parallel fashion between the controllers and the terminal block over respective data communication links. Signals output from the controllers are respectively fed via lines to common connection at a node. Interposing diodes are provided to prevent undesired backfeed. A similar terminal connection is employed for outputting a common signal to the three controllers.
There is room for improvement in apparatus and methods for providing hot standby operation with normal and standby processors.